Functional morphology of mucosal goblet cells based on spatial separation of orifice openings to the surface – Application to the rabbit bulbar conjunctiva

The purpose of the study was to assess spatial separation of goblet cell orifices observed at the surface of the rabbit bulbar conjunctiva by scanning electron microscopy (SEM) specimens of the bulbar conjunctiva from 8 healthy pigmented rabbits were obtained using a special preparation technique by which the tissue was carefully stretched out during glutaraldehyde fixation. On high magnification prints of SEM images of the conjunctival surface, the locations of goblet cell openings (orifices) to the apical surface were marked and the centre-to-centre spacing between all such orifices measured. Across the regions of interest (ROI), with averaged dimensions of 322 μm × 230 μm (adjusted for tissue shrinkage), the averaged value for the distances between all orifices was 196 μm (range 141–241 μm), with the calculated density of orifices being 412 mm−2. A sequential order-based analysis of the spatial separation between orifices indicated a predictable value of 6 μm, a separation that showed a nearly linear inter-dependence over distances of at least 200 μm. The openings of goblet cells to the surface of unstimulated bulbar conjunctiva have a organized spatial distribution that is consistent with there being an organized control of goblet cell secretion.